fix(admin): repair media upload redirect

app/admin/medien/page.tsx

@@ -1,20 +1,26 @@
-import { mkdir, readdir } from "fs/promises";
-import path from "path";
 import Image from "next/image";
 import { redirect } from "next/navigation";
 import AdminShell from "@/components/admin/AdminShell";
 import { requireAdminSession } from "@/lib/admin/auth";
+import { listMediaFiles } from "@/lib/admin/media";
 
-const uploadDir = path.join(process.cwd(), "public", "uploads", "images");
-
-async function getFiles() {
-  await mkdir(uploadDir, { recursive: true });
-  return readdir(uploadDir);
+function formatBytes(size: number) {
+  if (size < 1024) return `${size} B`;
+  if (size < 1024 * 1024) return `${(size / 1024).toFixed(1)} KB`;
+  return `${(size / 1024 / 1024).toFixed(1)} MB`;
 }
 
-export default async function AdminMediaPage() {
+function uploadErrorMessage(error?: string) {
+  if (!error) return "";
+  if (error === "missing-file") return "Bitte wählen Sie eine Datei aus.";
+  if (error === "storage") return "Die Datei konnte nicht gespeichert werden. Bitte Upload-Speicher und Rechte prüfen.";
+  return error;
+}
+
+export default async function AdminMediaPage({ searchParams }: { searchParams: Promise<{ uploaded?: string; error?: string }> }) {
   if (!await requireAdminSession()) redirect("/admin/login");
-  const files = await getFiles();
+  const [files, params] = await Promise.all([listMediaFiles(), searchParams]);
+  const error = uploadErrorMessage(params.error);
 
   return (
     <AdminShell>
@@ -22,25 +28,40 @@ export default async function AdminMediaPage() {
         <p className="eyebrow">Assets</p>
         <h1>Medienverwaltung</h1>
       </div>
+      {params.uploaded === "1" && <p className="success">Datei wurde erfolgreich hochgeladen.</p>}
+      {error && <p className="error admin-message">Upload fehlgeschlagen: {error}</p>}
       <form className="admin-card admin-upload" action="/api/admin/media" method="post" encType="multipart/form-data">
         <label>Datei hochladen<input name="file" type="file" accept="image/jpeg,image/png,image/webp,application/pdf" /></label>
         <button className="button" type="submit">Datei hochladen</button>
       </form>
       <section className="admin-card">
         <h2>Uploads</h2>
-        <div className="media-grid">
-          {files.map((file) => {
-            const url = `/uploads/images/${file}`;
-            return (
-              <a key={file} className="media-item" href={url} target="_blank" rel="noreferrer">
-                {/\.(png|jpe?g|webp)$/i.test(file)
-                  ? <Image src={url} alt={file} width={320} height={220} />
-                  : <span>{file}</span>}
-              </a>
-            );
-          })}
-          {files.length === 0 && <p className="admin-muted">Noch keine Uploads vorhanden.</p>}
-        </div>
+        {files.length === 0 ? (
+          <div className="media-empty">
+            <h3>Noch keine Medien vorhanden</h3>
+            <p>Hochgeladene Bilder und PDF-Dateien erscheinen hier mit Vorschau und Metadaten.</p>
+          </div>
+        ) : (
+          <div className="media-list">
+            {files.map((file) => (
+              <article key={file.name} className="media-row">
+                <a className="media-preview" href={file.url} target="_blank" rel="noreferrer">
+                  {file.isImage
+                    ? <Image src={file.url} alt={file.name} width={220} height={140} />
+                    : <span>{file.type}</span>}
+                </a>
+                <div>
+                  <h3>{file.name}</h3>
+                  <dl className="media-meta">
+                    <div><dt>Typ</dt><dd>{file.type}</dd></div>
+                    <div><dt>Größe</dt><dd>{formatBytes(file.size)}</dd></div>
+                    <div><dt>Upload</dt><dd>{new Date(file.uploadedAt).toLocaleString("de-DE")}</dd></div>
+                  </dl>
+                </div>
+              </article>
+            ))}
+          </div>
+        )}
       </section>
     </AdminShell>
   );